Single pot MC question

[jwh f-100]

Does the slick single pot have a residual pressure valve????

[daleshotrodshop]

Yes it does have a residual check valve. I think all hydraulic drum brakes use this valve a vacuum would result pulling air into the system without it.

[Alan Mclennan]

I might be wrong again, but I don`t think so!, isn`t that why there's a reserve?

[LM14]

The check valve is there to keep a slight pressure in the system, not as a vent.

Most drum brake systems are around 10# of pressure. That pressure keeps the shoes out closer to the drums so braking happens instantly when you hit the pedal and half of your pedal stroke isn't wasted moving the shoes out to the drum surface. Discs use a much lower valve or none at all because of the very small distance a pad needs to travel.

The venting is done thru a small hole close to the end of the piston bore. Watch the bubbles come up as you slowly move the pedal with the cap off and see where those bubbles come from.

SPark

[Uncle Skip]

There is no residual pressure valve on a Slick because the fluid reservoir is above the level of the cylinders and the fluid holds what pressure is needed on the brakes. This works because the fluid can't flow back uphill to the M/C. They used them in Effies because the master cylinder was on the same level as the brake cylinders and would bleed the pressure back.

[Toyz]

Seems to me that if the fluid can't travel back uphill, we be in BEEEG trouble!
Paul

[Toyz]

1961 Ford truck service manual: "A defective check valve can cause a loss of residual pressure in the system causing air to enter at the wheel cylinder piston"
Spring, valve, and valve seat are located in front of the master cylinder piston.
Paul